The present invention relates to a forging punch to be used for manufacturing a component such as a liquid ejection head. The present invention also relates to a minute forging method and a method of manufacturing a liquid ejection head using the same.
Forging work is used in various fields of products. For example, it is thought that a pressure generating chamber of a liquid ejection head is molded by forging metal material. The liquid ejection head ejects pressurized liquid from a nozzle orifice as a liquid droplet, and the heads for various liquids have been known. An ink jet recording head is representative of the liquid ejection head. Here, the related art will be described with the ink jet recording head as an example.
An ink jet recording head (hereinafter, referred to as “recording head”) used as an example of a liquid ejection head is provided with a plurality of series of flow paths reaching nozzle orifices from a common ink reservoir via pressure generating chambers in correspondence with the orifices. Further, the respective pressure generating chambers need to form by a fine pitch in correspondence with a recording density to meet a request of downsizing. Therefore, a wall thickness of a partition wall for partitioning contiguous ones of the pressure generating chambers is extremely thinned. Further, an ink supply port for communicating the pressure generating chamber and the common ink reservoir is more narrowed than the pressure generating chamber in a flow path width thereof in order to use ink pressure at inside of the pressure generating chamber efficiently for ejection of ink drops.
According to a related-art recording head, a silicon substrate is preferably used in view of fabricating the pressure generating chamber and the ink supply port having such small-sized shapes with excellent dimensional accuracy. That is, a crystal surface is exposed by anisotropic etching of silicon and the pressure generating chamber or the ink supply port is formed to partition by the crystal surface.
Further, a nozzle plate formed with the nozzle orifice is fabricated by a metal board from a request of workability or the like. Further, a diaphragm portion for changing a volume of the pressure generating chamber is formed into an elastic plate. The elastic plate is of a two-layer structure constituted by pasting together a resin film onto a supporting plate made of a metal and is fabricated by removing a portion of the supporting plate in correspondence with the pressure generating chamber. Such a structure is disclosed in Japanese Patent Publication No. 2000-263799A, for example.
Since the thickness of the partition wall is extremely thinned, it is hard to accurately obtain the recessed shape of the pressure generating chamber to uniformly set the liquid containing volume thereof. Since the recessed shape is generally elongated in many cases, the length of the partition wall is accordingly increased. For this reason, it is important that the partition wall is to be accurately fabricated over an entire length in order to uniformly maintain the liquid containing volume. In particular, it is important that the height of the partition wall is sufficiently maintained in a manufacturing stage in order to obtain proper recessed shapes of adjacent pressure generating chambers.
Meanwhile, according to the above-described related-art recording head, since a difference between linear expansion rates of silicon and the metal is large, in pasting together respective members of the silicon board, the nozzle plate and the elastic plate, it is necessary to adhere the respective members by taking a long time period under relatively low temperature. Therefore, enhancement of productivity is difficult to achieve to bring about a factor of increasing fabrication cost. Therefore, there has been tried to form the pressure generating chamber at the board made of the metal by plastic working, however, the working is difficult since the pressure generating chamber is extremely small and the flow path width of the ink supply port needs to be narrower than the pressure generating chamber to thereby pose a problem that improvement of production efficiency is difficult to achieve.